Refactor SDK span creation and implementation (#2213)

* Refactor startSpanInternal into a tracer method

The span creation and configuration process is split across the tracer
Start method and the startSpanInternal function, each living in
different files. This adds confusion when developing. It requires the
developer to remember certain parts of the configuration happen in one
place or the other.

This unifies the creation and configuration of a new span. It makes this
unification by creating a newSpan method on the tracer. This method will
do all the configuration needed for a new span other than setting the
execution task tracker. This remains a part of the Start method to
preserve any existing timing and tracing the already exists.

* Add a non-recording span to the SDK

* Assign returned context from runtime trace task

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>